Reading this question How fast does gravity propagate?, I'm curious over the consequences of the sun being removed.

As should be clear, we cannot just remove the sun as it violates energy conservation. We can however let the Sun accelerate fast (but subluminal) out of the solar system.

Assuming this (unreasonable) scenario, will this fast disappearance of Sun cause any gravitational wave signature? Basically would and experiment such as LIGO be able to measure a gravitational signature of the Sun's removal.

INTUITION: The intuition I'm having here is that if the Sun is removed quickly there could be ripples in the space-time in the wake of the Suns path out of the solar-system, and these could be detected.

  • $\begingroup$ Aren't you basically asking if an accelerating object creates gravitational waves? In which case see Does an object creates gravitational waves when only accelerating in one direction? $\endgroup$ – John Rennie Oct 20 '16 at 15:33
  • $\begingroup$ Your Intuition is true. $\endgroup$ – Physics Guy Oct 20 '16 at 15:34
  • 2
    $\begingroup$ We have plenty of instruments that can measure the removal of the sun. $\endgroup$ – gerrit Oct 20 '16 at 15:44
  • $\begingroup$ @JohnRennie I suppose i am, than you for pointing that out. $\endgroup$ – Mikael Fremling Oct 21 '16 at 8:54
  • $\begingroup$ Basically would and experiment such as LIGO be able to measure a gravitational signature of the Sun's removal. - Even I myself, sitting on the sofa in my apartment, would be able to measure the gravitational signature of the Sun's removal :) Gravitational waves aren't the only kind of observable effects of such an event. $\endgroup$ – Prof. Legolasov Oct 21 '16 at 12:00

The linear acceleration of the sun would indeed cause gravitational waves - it is the acceleration of mass that does so provided that the mass distribution is not spherical.

But, if the mass is truly spherically symmetrical it can expand/contract as fast and as much as you want and no gravitational waves will be emitted. This is due to Birkhoff's Theorem (Wikipedia link).

So if the sun were to be removed by accelerating all its mass outwards but in a spherically symmetric way (as though it exploded very neatly) no gravitational waves would be generated.

Gravitational waves are however expected from real explosions such as supernovae because the mass distribution is not perfectly spherically symmetric - as evidenced by the observed residual motion "the supernova kick" of remnant neutron stars and the forms of supernova-generated nebulae.


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